openclaw - 💡(How to fix) Fix Bug: Orphaned tool_result after API error mid-tool-call corrupts session permanently [4 comments, 2 participants]

Bug: Orphaned tool_result after API error mid-tool-call corrupts session permanently

Description

When the Anthropic API returns an error (e.g., overloaded_error) mid-tool-call, the session becomes permanently corrupted with an orphaned tool_result that references a malformed tool_use block.

Reproduction

1. Start a tool call that streams a response
2. API returns overloaded_error (or api_error, timeout, etc.) mid-stream
3. Assistant message is saved with stopReason: "error" and an incomplete tool_use block containing partialJson
4. session-tool-result-guard.js detects the pending tool call ID and inserts a synthetic tool_result
5. Every subsequent API request fails with:

   messages.X.content.Y: unexpected tool_use_id found in tool_result blocks: toolu_XXXX
   Each tool_result block must have a corresponding tool_use block in the previous message.

Root Cause

In session-tool-result-guard.js and session-transcript-repair.js, the extractAssistantToolCalls() / extractToolCallsFromAssistant() functions extract tool calls based only on:

• rec.type === "toolCall" (or toolUse/functionCall)
• rec.id being a valid string

They do NOT check for the partialJson field, which indicates the tool call was truncated mid-stream and is incomplete/malformed.

The Fix

Add a check to skip tool calls with partialJson:

if (rec.type === "toolCall" || rec.type === "toolUse" || rec.type === "functionCall") {
    // Skip incomplete tool calls (truncated by API error mid-stream)
    if (rec.partialJson !== undefined) {
        continue;
    }
    toolCalls.push({
        id: rec.id,
        name: typeof rec.name === "string" ? rec.name : undefined,
    });
}

Apply to both:

• dist/agents/session-tool-result-guard.js (line ~13-20)
• dist/agents/session-transcript-repair.js (line ~12-17)

Affected Error Types

Workaround

For already-corrupted sessions, move the session file:

mv ~/.clawdbot/agents/main/sessions/SESSION_ID.jsonl ~/.clawdbot/agents/main/sessions/SESSION_ID-BROKEN.jsonl

Environment

• clawdbot version: 2026.1.24-3+
• Provider: Anthropic
• Model: claude-opus-4-5